1. Field of the Invention
The present invention relates to a backlight device, and more particularly, to a backlight device for use in a liquid crystal display (LCD) device.
2. Description of Related Art
FIG. 1 shows a conventional backlight device for use in an LCD device. As shown in FIG. 1, the conventional backlight device 100 includes a light source 10, a U-shaped lamp holder 15 having a lamp reflector 16, a light waveguide plate 40, a reflector 50, and a prism sheet 20. The light source 10 is located adjacent to an end 40a of the light waveguide plate 40, and most of the light source 10 is surrounded by the lamp holder 15. The end 40a constitutes a surface through which the incident light from the light source 10 is emitted. The prism sheet 20 is arranged on a front surface 40b of the light wave guide plate 40, and the reflector 50 is located under a bottom surface 40c of the light wave guide plate 40.
The emitted light from the light source 10 is directed toward the surface 40a of the light waveguide plate 40 by the lamp reflector 16 and is then directed either toward a prism sheet 20 or a reflector 50. The light reflected by the reflector 50 is emitted toward the observer through a prism sheet 20, and a liquid crystal panel (not shown) in the form of an information.
FIG. 2 is a graph illustrating brightness with respect to an angle of light passing through the prism sheet. As shown in FIG. 2, brightness distribution is discursive. In other words, light passing through the prism sheet 20 is not well collimated. As a result, light collimating efficiency is bad, and collimating loss takes place at portions “A”. In addition, in the conventional backlight device of such a structure, it is not easy to narrow an angle of light passing through the prism sheet to a desirable angle range (for example, from −40 degrees to +40 degrees).
For the foregoing reasons, there is a need for a backlight device having a high light collimating efficiency.